Food processing plants typically must be cleaned at regular intervals to comply with various governmental regulations intended to ensure food safety. In many food processing plants, this entails shutting down at least a portion of the plant and manually cleaning the plant using various detergents. In many cases, the detergents are applied by cleaning personnel via a hose or the like. In other cases, a fixed cleaning system including an array of nozzles may automatically wash down the plant.
In either case, during cleaning the potential exists for water and/or detergent solutions to enter electrical boxes within the plant associated with the food processing equipment. Since electrical components typically do not fare well when exposed to moisture, it is common to provide such electrical boxes with gaskets and other sealing elements in an attempt to make them waterproof. Regardless of such efforts, however, the opportunity remains for moisture to enter the boxes.
To address this issue, some food processing plants supply a stream of dry compressed air to each electrical box. Since compressed air is generally moisture-laden, membrane air dryers have been employed to dry the air after it is compressed. The dry air is then circulated through the boxes to absorb and remove any moisture therein.
Such dryers are known in the art of compressed gas systems and are devices that remove water from a compressed air system, specifically the water that exists in the vapor phase. The performance of such air driers, which typically contain a membrane module, is generally measured by the dewpoint suppression achieved as air passes through the module. The dewpoint is the temperature at which moisture will start to condense out of the moist air. Dewpoint suppression is the number of degrees the dew point is lowered as the air passes through the drier.
The dewpoint suppression is a function of the membrane area, feed flow rate, operating pressure and temperature, and sweep fraction. Membrane air dryers typically function by contacting one side of a semi-permeable membrane with a pressurized wet feed stream. The membrane preferentially allows water vapor to permeate therethrough resulting in a drying of the compressed air stream. A portion of the dried gas, commonly referred to as the “sweep”, is fed back to contact the other side of the membrane and acts to sweep away the water moisture that has permeated the membrane. The sweep is often controlled by an externally mounted valve or an internal orifice. Such dryers typically employ an external valve or pressure regulator for controlling the flow of compressed air through the dryer.